Improvements relating to the moulding of foundry casting, particularly for light alloys



May 15, 1956 R. LUCIEN ET AL 2,745,154

IMPROVEMENTS RELATING TO THE MOULDING OF FOUNDRY CASTING, PARTICULARLYFOR LIGHT ALLoYs Filed Jan. 4, 1951 NYVE/ITORK YED/c150; A.

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United States Patent IMPROVEMENTS RELATING TO THE MOULDING OF FOUNDRYCASTING, PARTICULARLY FOR LIGHT ALLOYS Application January 4, 1951,Serial No. 204,318 Claims priority, applicationFrance May 2, 1950 3Claims. (Cl. 22-134 The invention relates to a process of casting whichis known in metallurgy as bottom-casting, according to which a metalenters a mould from the lower part thereof and then rises slowly thereinunder the inclosed gases and impurities.

In the accompanying drawing:

Figure 1 is a diagrammatic sectional view of a mould prepared forbottom-casting in known manner.

Figures 2 and 3 are enlarged sectional views of two examples of elementsprovided for use in such a mould in accordance with the presentinvention.

With reference to Figure 1 it is to be noted that in the bottom-castingprocess there is utilised a moulding box a comprising a runner cup b bywhich metal is poured into a down runner c, which is substantiallyvertical, to a feed runner d arranged in the lower part of the mouldingbox. At the gate e of this runner, the desired upward entry of the metalto the casting space P occurs.

It is known that, for the casting of light alloys that are verysusceptible to oxidation, the foundryman generally uses bottom castingbecause it is the least disturbing casting process and because it ofiersknown advantages relative to other casting processes.

It is known, on the other hand, that for the casting of metals having asubstantial liquid shrinkage, it is common to arrange, over the work tobe fed, one or several air holes 1, that, on the cooling of the work,continue protecting risers allowing the gases to escape and formingstores of liquid metal that feed the casting during its liquid shrinkageto allow the obtaining of sound castings.

It is also known that, while it is possible to determine with asufficiently close approximation the volume of liquid metal necessaryfor feeding a casting P, having a given volume, it is, very difficult tocontrol the cooling of the risers 1 during the duration of the liquidcooling of the casting. Now, at the instant when bottom casting isstopped, the metal is much hotter in the lower part of the casting thanin the risers. Accordingly, in order that the risers assume theirfunction of feeding, it is necessary to delay as much as possible thecooling thereof.

An object of the invention is therefore to provide for insulating therisers from the sand which surrounds them by means such as a sheath madein the form of a double envelope filled with an appropriate insulatingmaterial, for example glass wool or the like.

In Figures 2 and 3 are respectively shown, in cross section, twoinsulating sheaths for foundry risers according to the invention and asshown by the member g in Fig. 1.

The sheath is constituted by a double envelope, 1-2, the inner volume 3of which is filled with insulating material. The internal space 4, whichis reserved for the riser can advantageously be in the form of atruncated cone, the larger base of which is arranged at the bottom ofthe riser whereas the outer envelope 2, also has the shape of atruncated cone, the larger base of which is arranged at the top of theriser.

Patented May 15, 1956 This heat-insulated envelope can also be easilyremoved from the mould after the liquid shrinkage of the casting iscompleted, by lifting the handle 5, leaving thus full latitude for thecasting to make its solid contraction without fear of the formation offlaws. The trimming of the casting is moreover greatly facilitated.

In the embodiment shown in Figure 2', the sheath is open to theatmosphere at 6 whereas, in the embodiment of Figure 3,- the sheath onlyhas a narrow orifice 7 for the escaping of the gases.

' The volume of the insulating mass 3 and more partic- "ice ularly itsmean thickness are determined in accordance with the conductibility ofthe insulating material chosen, in order to assure a time ofsolidification of the metal in the riser which is greater than the timeof solidification of the material of the casting contained in the mould.

' Moreover, the volume of the riser, that is to say, of the space4, willbe determined in accordance with the volume of the casting to be fedduring its solidification.

In order to reduce to a minimum the volume of the riser, the heat sheathcan advantageously be provided, without departing from the scope of theinvention, with means for heating it, for example electrically, by meansof a resistance arranged in the insulating material 3.

The invention can be put into practice in the casting shop by means of aseries of heat insulated sheaths of suitable number and dimensions,formed as a standard stock of tools, which can be conveniently taken upin to be poured and taking account of the need which exists for thefeeding of each piece. The sheaths are arranged in the sand of themoulding box and about the orifice provided for the riser.

By the application of the process according to the invention and of theabove described stock of tools, one

can obtain in particular in the moulding of castings in light metals andof high mechanical resistance, characteristics entirely comparable withthose which are obtained, by the employment in current technology, ofmuch more bulky risers.

We are aware that it already has been proposed to provide with a heatinsulated sheath the cups used in drop casting.

In said drop casting, substantially different from bottom casting as itconsists of feeding the work by the upper part of the moulding box, theriser for feeding the shrinkage of the work to be moulded is usually andpreferably formed by the runner cup itself. Now, said runner cup beingfilled last, that is at the end of the pouring, and consequentlycontaining the hottest part of the metal, normally is in good conditionfor feeding with liquid metal the work during its cooling. The provisionof a heat insulated sheath is practically useless in this instance.

On the contrary, in the process of bottom casting, the heat insulatedsheath arranged in the risers is essential for the upper parts of thework to be constantly fed by liquid metal maintained at a suitabletemperature. Moreover, the provision of heat insulated sheaths on therunner cups used in drop casting would be of no interest.

These differences, on the one hand in the location of the sheaths and onthe other hand in the casting processes to which they are respectivelyapplied, dillierentiate in its principle the present invention from theprevious process.

We claim:

1. In combination with a bottom casting mould having an outer sand boxwith an outwardly flared vent therein, a heat-insulating sheathpositioned in the vent and comprising a pair of hollow frusto-conicalmembers positioned one inside the other defining an inner space for theescape of gases from the inside of the mould and the formation of ariser and an intermediate space between the two members, the outer oneof said members flaring upwardly and the inner one downwardly, and amass of insulating material in said intermediate space having a greaterheat resistance than the sand in the box surrounding the vent, thehollow frusto-conical members constituting an integral unit adapted tobe readily removed from the vent.

2. A heat-insulating sheath according to claim 1, wherein the upper,smaller end of the inner one of said members is entirely open.

3. A heat-insulating sheath according to claim 1 wherein the upper,smaller end of the inner one of said members is shaped to define anarrow, gas escape hole, and wherein said insulating material extendsacross said end around said hole.

References Cited in the file of this patent UNITED STATES PATENTS1,218,438 McNaughton Mar. 6, 1917 Carroll Feb. 25, 1902 20 4 BrunnerSept. 16, 1919 Durville May 4, 1926 Trembour Jan. 1, 1929 Gathmann Dec.10, 1929 Williams et al Nov. 27, 1934 Lewis Dec. 8, 1936 Seaver July 11,1939 Lindemuth Dec. 19, 1939 McWane Jan. 9, 1940 Johnston Jan. 21, 1941McDonald Feb. 11, 1941 Dornduf Feb. 9, 1943 FOREIGN PATENTS GreatBritain Feb. 26, 1931 Great Britain May 31, 1934 Great Britain July 28,1947 Great Britain Nov. 22, 1950 OTHER REFERENCES

1. IN COMBINATION WITH A BOTTOM CASTING MOULD HAVING AN OUTER SAND BOXWITH AN OUTWARDLY FLARED VENT THEREIN, A HEAT-INSULATING SHEATHPOSITIONED IN THE VENT AND COMPRISING A PAIR OF HOLLOW FRUSTO-CONICALMEMBERS POSITIONED ONE INSIDE THE OTHER DEFINING AN INNER SPACE FOR THEESCAPE OF GASES FROM THE INSIDE OF THE MOULD AND THE FORMATION OF ARISER AND AN INTERMEDIATE SPACE BETWEEN THE TWO MEMBERS, THE OUTER ONEOF SAID MEMBERS FLARING UPWARDLY AND THE INNER ONE DOWNWARDLY, AND AMASS OF INSULATING MATERIAL IN SAID INTERMEDIATE SPACE HAVING A GREATERHEAT RESISTANCE THAN THE SAND IN THE BOX SURROUNDING THE VENT, THEHOLLOW FRUSTO-CONICAL MEMBERS CONSTITUTING AN INTEGRAL UNIT ADAPTED TOBE READILY REMOVED FROM THE VENT.